For historical converter information:
My Progressive Dynamics PD-808 deck mount converter, circa 1970, floats at 13.4V ->13.5 V. It has an accessory adder circuit board to enable it to have two stage battery charger function. This was an option that PD developed to make the converter something other than a power supply. The literature of the day suggests that even having a power supply was a luxury at that time. Having an effective battery charging circuit was an even newer development.
What's really cool about this PD-808 is that it works flawlessly. There is not a flicker or deviation in voltage that I could detect. That most likely is because of the large transformer and discrete rectifier section with big heat sink.
